Ropes and cordage



United States Patent 3,402,547 ROPES AND CORDAGE Michael Richard Parsey, Harrogate, England, assignor to Imperial Chemical Industries Limited, Millbank, London, England, a corporation of Great Britain No Drawing. Filed Jan. 24, 1966, Ser. No. 522,407 Claims priority, application Great Britain, Feb. 2, 1965, 4,526/65; Jan. 11, 1966, 1,138/66 7 Claims. (Cl. 57-140) ABSTRACT OF THE DISCLOSURE Multi-strand laid rope and the like having a combination of desirable properties is made of films, ribbons, filaments or fibres of steroregular polypropylene.

This invention relates to ropes and other cordage produced from films, ribbons, filaments or fibres composed of stereoregular polypropylene.

Since the introduction of synthetic fibres made from linear thenrnoplastic polymers with their inherent uniformity, high strength and increased abrasion resistance, many attempts have been made to replace natural fibres with the synthetic fibres. In the rope and cordage industry, for example, synthetic fibres, produced by melt spinning in continuous filament form, have been utilised in this form for the production of twine and rope by subjecting the yarns to a number of plying operations or by making the rope with a special construction, as for example, a twistless core surrounded by a braided sheath. Ropes and twine have also been produced from other forms of synthetic polymers, as for example, films and slit-films or ribbon filaments. Of the many processes and types of ropes produced hitherto some have possessed advantages in one direction and others advantages in another direction but none have possessed in combination more than a few of the properties required in an ideal rope. We have now produced a rope possessing a unique combination of desirable properties, which combination achieves a much closer approach to the ideal than any rope produced hitherto.

According to the present invention we provide ropes composed of films, ribbons, filaments or fibres of stereoregular polypropylene having a combination of properties which in the form of the standard 3 inch (7.6 cm.) circumference laid rope are (l) A stretch resistance at 5,000 lbs. (2268 kg.) load of at least 400 lbs. (181 kg.) per 1% extension, (2) a torque resistance of at least 50 in.-lb. (0.58 kg.-m.) per revolution, per tan strand helix angle, (3) a creep after 120 repeat loadings to 75% of the breaking load of less than and (4) a breaking load of at least 7.75 tons (7874 kg).

With the exception of the creep measurements all properties are those measured on the first loading of the rope specimens.

We have described the distinctive properties of the ropes we have produced in terms of the usual standard of assessment and comparison of ropes in the rope industry, namely what is termed a 3 inch circumference rope, which is a rope having a measured circumference of 3 inches (7.6 cm.) under a load of 154 lb. (70 kg.). Such ropes when made of circular filaments of polyproplyene have a weight per 100 ft. of 18.0 lb. (8.2 kg. per 30.5 m.)

3,402,547 Patented Sept. 24, 1968 and when made of slit film tapes or ribbon filaments have a weight per ft. of 18.5 lb. (8.4 kg. per 30.5 m.). The unique combination of properties is not confined to 3" (7.6 cm.) circumference ropes but is achieved in smaller and larger ropes and cordage if care is taken to select the filaments or fibres and rope yarns used in their construction according to the principles hereinafter described. Values of stretch and torque resistance, creep and breaking load found using rope specimens other than the standard 3 inch (7.6 cm.) laid rope may be expressed in terms of the standard rope by adjustment of the measured value in the following ways.

(a) Torque resistance.-The value found, multiplied by 18.0/w or 18.5/w for ropes composed of circular filaments or slit film tapes and ribbon filaments respectively (:0 is the weight per 100 feet of the specimen) gives the corresponding value in terms of the 3 inch circumference rope. The corresponding factors in metric units are 8.2/w and 8.4/w where w is the specimen weight (kg.) per 30.5 metres.

(b) Breaking l0ad.-The value found is adjusted using the values found for the weight (measured) per 100 ft. (30.5 metres) of the specimen and the Weight and breaking load obtained from Table 1 or Table 2, presented hereinafter, depending whether the material of which the rope is made is circular filaments (Table 1) or film tapes or ribbon filaments (Table 2). The adjusting calculation is expressed;

Adjusted breaking load=A-% TABLE 1.-FOR BOP??? COMPOSED OF CIRCULAR LAMENTS Weight Breaking load For 100 ft. (lb.) Per 30.5 in. (kg) Tons Kg.

TABLE 2.FOR ROPES COMPOSED OF FILM TAPES OR RIBBON FILAMENTS Weight Breaking load Per 100 ft. (lb.) Per 30.5 111. (kg) Tons Kg.

(0) Stretch resistance.The value found is adjusted using the values found for the weight (measured) per 100 feet (30.5 metres) of the specimen and the weight and stretch resistance obtained from Table 3 or Table 4, presented hereinafter, depending whether the material of which the rope is made is circular filaments (Table 3) or film tapes or ribbon filaments (Table 4). The adjusting calculation is expressed;

Adjusted stress resistance 0 where C is the measured stress resistance, D and D are the values of stress resistance found from the appropriate table for the standard 18.0 lb. (8.2 kg.) (circular filaments, Table 3) or 18.5 lb. (8.4 kg.) (tapes etc., Table 4) rope and a rope of the same weight as the specimen, respectively; the units being consistent.

TABLE 3.FOR ROPES COMPOSED OF CIRCULAR TABLE 4.FOR ROPES COMPOSED OF FILM TAPES OR RIBBON FILAMENIS Weight Stretch resistance Per 100 ft. (lb.) Per 30.5 m. (kg) In order that the unique combination of properties should be attained we have found it necessary to control certain properties in the rope yarns from which the rope strands and thence the ropes are constructed and we have found that these requirements differ slightly depending whether the rope yarns are prepared from filaments or fibres on the one hand or from films, as for example, by

. 4 I slitting into strips before or after drawing, or ribbon filaments on the other.

We prefer to use a rope yarn, prepared from continuous filaments of polypropylene, to have a friction of at least 2 lb. (910 g.) and a resilience (R) depending upon the rigidity (r) of the yarn as follows;

For (r) 1200-2000 g. wt. cm. (R) is preferred to be in the range 50-65 For (r) 600-1200 g. wt. cm. (R) is preferred to be in the range 65-85%.

Likewise we prefer to use a rope yarn, prepared from slit films or ribbon filaments of polypropylene to have a friction of 4.5-40 lb. (2.04-18.14 kg.), preferably 10-30 1b. (4.54-13.61 kg.) and preferably also a resilience and rigidity as follows;

For (r) 200-600 g. wt. cm. (R) is preferably in the range -l00%.

For (r) 600-1200 g. Wt. cm. (R) is preferred to be in the range 6585%.

We have found in the case of rope yarns prepared from films or ribbon filaments of polypropylene that it is very desirable to keep the friction of rope yarns in the foregoing range in order that the unique combination of properties may be achieved in the rope. Thus if the rope yarn friction is less than 4.5 lb. (2.04 kg.) the desired values of torque resistance and strength are unlikely to be realised and if the friction exceeds 40 lb. (18.14 kg.) the desired strength and stretch resistance values are unlikely to be attained in the rope.

It is further desirable, although not essential, that ropes possessing a unique combination of properties according to this invention should have a weight for feet of less than 18.5 lb. (8.4 kg.) for this will give improved runnage and easier handling of large coils. For example, it has been found in practice that the number of men required to handle fathom (220 metres) coils of rope as used in the mooring of a large vessel, may be reduced from eight to five.

By the terms cordage or other cordage, used herein, we mean structures of lesser complexity than strand laid rope, as for example, twine, which comprises simply a small number of yarns twisted together. If yarns are prepared having the foregoing properties then the properties of even simple cordage will be enhanced also.

Ropes and other cordage according to this invention may be produced by submitting to the usual cordage or rope making processes, slit-films, ribbons, filaments or fibres composed of stereoregular polypropylene, which films etc. have been melt-extruded and then uniaxially drawn in the solidified state to a draw ratio of at least 13:1 and have in the drawn condition a thickness (i.e. thickness or diameter of ribbon or filament respective- 1y) of at least 0.003 inch (0.008 cm.), preferably 0.005 inch (0.013 cm.). The drawing may be carried out in more than one stage in which case the total draw ratio applied should be at least 13:1. Filaments etc. which have been subjected to a high draw ratio may show a tendency to break longitudinally into fibrils. Such fibrillation, however, is not essential to achieve the unique combination of rope properties, neither is it deleterious if it should occur before or during the rope construction.

In laying ropes from rope yarns composed of slit film tapes or ribbon filaments, which yarns may be somewhat variable in denier along their lengths, it is desirable to ensure that a constant compressive force is applied to the strands during the laying process in order that the friction between rope yarns in the strand, and hence the rope strength, is uniform along their length. Likewise some benefit in terms of the resistance to abrasion and surface fusion of ropes and cordage according to the invention may be obtained by the application of a lubricant to the filaments etc., the rope yarns or the finished ropes but care must be taken to ensure that insufficient lubricant is added to delcteriously affect the rope properties. Particularly useful lubricants are the non- 5 drying vegetable oils described in British patent application No. 35,528/64.

The definition andmeasurement of the several physical terms used herein are as follows;

(1) Breaking lad.-The test machine described in British standard specification No. 2052 is used, using lead wedges to clamp the specimen in the machine instead of knotting the ends of the rope.

(2) Stretch resistance.--This is the slope of the load/ extension curve found in the breaking load measurement.

(3) Creep.This is the non-recovered extension (expressed as a percentage of the original length) in the specimen immediately after 120 repeat loadings to 75% of the breaking load, each loading being applied for 30 secs. with an interval of 30 secs. between the loadings.

(4) Torque resistance.-This is measured by means of a device which clamps the end of a rope specimen 6" long (15.24 cm.) under a fixed load of 9 lbs. (4.1 kg.) (for ropes up to inches (12.7 cm.) circumference) and records the torque required to twist the specimen through 1 revolution of one clamp in successive steps of 0.25, 0.5, 0.75 and 1.0 revolution. The value found after 1 revolution, normalised by dividing by the value of tan strand helix angle, is described as the torque resistance of the specimen, measured in inch-lb. (or kg.-m.) per revolution per tan strand helix angle. For ropes greater than 5 inches (12.7 cm.) circumference the rope specimen 2 feet (61 cm.) long is rigidly fixed at one end and held straight under a load of approximately 30 lb. (13.6 kg.). A 3 feet (91 cm.) long Marlin spike is inserted between the rope strands so that 2 feet (61 cm.) of it protrude and a spring balance is used to measure the load required to turn the spike through 90, the value found is then expressed as the torque in inch-lb. (or kg.-m.) per revolution per tan strand helix angle.

(5) Friction.This property is measured by securing the outer periphery of one end (4 inches long) (10.2 cm.) of an 8 inch (20.3 cm.) rope specimen to a cardboard cylinder,.enclosing but not compressing the specimen, with a heat hardenable epoxy resin as for example Araldite (regd. trademark) adhesive, heating the specimen for 1 hour at 70 C. to set the adhesive, unravelling the 3 strands, separating a central rope yarn from one of the strands and measuring the load required to withdraw this yarn from the strand by means of a machine as used in measuring breaking load to the nearest 0.5 lb. (277 g.). The measurement is repeated on the other rope strands and the mean value recorded. 7

(6) Rigidity-This property is measured by torsion pendulum using a 9 inch (22.9 cm.) long specimen of rope yarn (having a twist level of turns per inch times /denier=200) from which a cylindrical weight is suspended horizontally at its centre. The weight is 128 gm. (0.29 lb.) and measures 13 inches (33 cm.) long by 0.16 inch. (0.4 cm.) diameter and the period of oscillation is measured using an amplitude of $180.

(7) Resilience.This property is measured using a inch (25.4 cm.) long specimen of rope yarn (having a twist level of turns per inch times /denier=200) and a Goodbrand Twist Tester as used in B.S.S. 2085. The rope yarn specimen is inserted into the 'Iwist Tester and the twist level is doubled. After holding in this state for 30 seconds one end of the specimen is released and the twist allowed to run out for 5 seconds after which the free end is reinserted in the tester and the level of twist remain- Example 1 Isotactic polypropylene is melt spun at 250 C. into monofilaments which are subsequently drawn in two stages at 100 C. and 135 C. using an overall draw ratio of 14:1 to filaments having a diameter of 0.015 inch. A 3-strand laid rope is prepared from this material on convention-al rope-making equipment using 3/ 45 16 construction and twists, measured on the completed structure, of 0.27 turn per inch Z (rope), 0.40 S (strand) and 1.0 Z (rope yarn) (10.6, 15.7 and 39.4 turns/ meter respectively). The deniers of rope, strand and rope yarn are 2.7 10 6.8 10 and 1.36X10 respectively, The rope thus produced has a weight per 100 ft. of 18.5 lb. (8.4 kg. /30.5 m.) and the following properties, expressed in terms of the standard 3 inch (7.6 cm.) circumference rope;

(a) Stretch resistance.250 kg./ percent extension.

(b) Torque resistance.0.7 kg. metre per revolution, per tan strand helix-angle.

(c) Creep.12%.

(d) Breaking l0ad.7.8 tons (7925 kg.).

A single rope yarn has a rigidity of 1178 grams weight centimetres, a resilience of and a frication of 2.4 lb. (1090 g.).

Example 2 Isotactic polypropylene is melt spun at 265 C. into ribbon filaments which are subsequently drawn by passage through and electrically heated radiant heater at a draw ratio of 13:1 to ribbon filaments having a width of 0.57 inch (1.4 cm.) and a thickness of 0.0035 inch (0.009 cm.). A 3 strand laid rope is prepared from this filament using a construction of 3/ 28/ 2 and twists, measured on the completed structure of 0.27 turn per inch Z (rope), 0.40 turn per inch S (strand) and 0.725 turn per inch Z (rope yarn) (10.6, 15.7 and 28.6 turns/metre respectively). The measured deniers of rope, strand and rope yarn are 2.5 10 6.9 10 and 2.3 10 respectively. The rope thus produced has a weight per 100 ft. of 18.6 lbs. (8.5 kg./ 305 m.) and the following properties, expressed in terms of the standard 3 inch (7.6 cm.) circumference rope;

(a) Stretch resistance.-570 lbs. (260 kg.) per percent extension.

'(b) Torque resistance.l09 inch/lb. (1.26 kg.-metre) per revolution per tan strand helix angle.

(0) Creep.-10%.

(d) Breaking l0ad.-8.3 tons (8433 kg.).

The rope yarn has a rigidity of 531 gram weight centimetres, a resilience of and a friction of 14.2 lb. (5.81 kg.).

Comparative Example A A 3-strand laid rope, prepared from isotactic polypropylene ribbon filaments of similar construction to that of Example 2, said filaments having a thickness of 0.0045 inch (0.011 cm.) and having been drawn to a draw ratio of 8.75:1, had a weight per 100 ft. of 18.8 lbs. (8.6 kg./30.5 m.) and the following properties expressed in terms of the standard 3 inch (7.6 cm.) circumference rope;

(a) Stretch resistance.303 lbs. (138.5 kg.) per percent extension.

(b) Torque resistance.255 inch/lb. (2.95 k-g.-metre) per revolution per tan strand helix angle.

(c) Creep.16%.

(d) Breaking l0ad.-6.5 tons (6604 kg.).

The rope yarn has a rigidity of 720 gram Weight centimetres, a resilience of and a friction of 15.7 lb. (7.12 kg.).

Comparative Example B Isotactic polypropylene is melt spun as in Example 1 but is drawn to a draw ratio of only 11:1, The drawn filaments are used to prepare a 3-strand laid rope of the same weight per ft., 18.5 lb. (8.4 kg./30.5 m.) as the rope of Example 1 using a 3/30/4/22 construction and twists, measured on the completed structure, of 3.6 Z (rope), 3.6 S (strand) and 22.8 Z turns per foot (rope yarn) (11.7, 11.7 and 7 4.3 turns/metre respectively). The measured denier of strand and rope yarn are 7.4 10 and Example 3 Isotactic polypropylene is melt spun and drawn as in Example 2. A 3-strand laid rope is prepared from this material employing special care to ensure uniformity of compression during the laying process and a 3/26/ 26,070 denier construction with twists, measured on the completed structure, of 3.9 Z (rope), 3.6 S (strand) and 10.8 Z turns per foot (rope yarn) (12.7, 11.7 and 35.1 turns/ metre respectively). The measured denier of strand and rope yarn are 7.5 10 and 2.6 10 and the weight of the rope is 19.0 lb. per 100 ft. (8.6 kg. per 30.5 metres). The rope thus produced has the following proper ties expressed in terms of the standard 3 inch (7.6 cm.) circumference rope;

(a) Stretch resistance-410 kg. per percent extension.

(b) Torque resistance.2.75 kg. metre/ revolution/ tan strand helix angle.

() Creep.13%.

(d) Breaking l0ad.8.6 tons (8738 kg.).

A single rope yarn has a rigidity of 1016 g. wt. cm., a resilience of 83% and a friction of 15.7 lb. (7.1 kg.).

Example 4 Slit film tapes are prepared by melt extrusion and drawing of isotactic polypropylene as in Example 2 cut the strand is 1.8 10 The rope thus produced has a weight per 100 feet of 46.6 lb. (21.1 kg. per 30.5 m.) and the following properties, the corresponding properties in terms of the standard 3 inch (7.6 cm.) circumference rope being shown in parentheses after each value;

(a) Stretch resistance.-53O (208) kg. per percent extension.

(b) Torque resistance-4.8 (1.78) kg. in. per revolution per tan strand helix angel.

(c) Creep.-14%.

(d) Breaking l0ad.-20,422 kg. (8,026 kg.).

Comparative Examples C and D Friction, lb. (kg) 4.2 75.4 Rigidity. g. \Vt. em.. 487 Resilience, percent 87 The properties of the two ropes expressed in terms of the standard 3 inch (7.6 cm.) circumferential rope were;

(a) Stretch resistance, kgJpercent extension. 285 162 (b) Torque resistance, kg./m./rev. tan strand helix angle 2. 1. 23 (e) Creep, percent 13.4 ((1) Breaking load, kg 6,807 4,267

Comparative Examples E-H In Table 5 are given average values for known ropes of various types, all properties being expressed in terms of the standard 3 inch (7.6 cm.) circumference rope.

1 Minutes.

ting the drawn film into tapes 0.57 inch (1.4 cm.) wide and 0.004 inch (0.010 cm.) thick. This material is used to prepare a 4-strand laid rope with a 4/ 34/ 12,360 denier construction and twists, measured on the completed structure, of 3.75 Z (rope), 4.0 S (strand) and 10.8 Z turns per foot (rope yarn) (12.2, 13.0 and 35.1 turns/metre respectively). The measured denier of strand and rope yarn are 4.6 and 1.2 X10 respectively and the weight of the rope is 16.6 lb. per 100 ft. (7.5 kg./30.5 metres). The rope thus produced has the following properties expressed in terms of the standard 3 inch (7.6 cm.) circumference rope;

(:1) Stretch resistance.-400 kg. per percent extension.

(b) Torque resistance.-2.7O kg. m./revolution/tan strand helix angle.

(c) Creep.14%.

(d) Breaking load.8.5 tons (8636 kg.).

The rope yarn has a rigidity of 1021 g. wt. cm., a resilience of 83% and a friction of 11.2 lb. (5.0 kg.).

Example 5 A 3 strand laid rope of 5 inches (12.7 cm.) circumference is prepared from film tape, as used in Example 4, with a 3/65/25,640 denier construction and twists, measured on the completed structure, of 0.2 Z (rope), 0.2 S (strand) and 0.85 Z turns per inch (rope yarns) (7.9, 8.9 and 33.4 turns/m. respectively). The measured denier of Comparative Example J In British patent specification 986,755 a process for the production of ropes from synthetic filaments of 0.001- 0.020 inch (0002-0051 cm.) diameter cut into -80 inch (63.5203.2 cm.) lengths is described. A rope of this kind prepared from isotactic polypropylene melt spun and subjected to a draw ratio of 15:1 (drawn filament diameter 0.0045 inch, 0.011 cm.) has the following properties expressed in terms of the standard 3 inch (7.6 cm.) circumference rope;

(a) Stretch resistance-280 kg./percent extension.

(b) Torque resistance.1.49 kg./m./rev./tan strand helix angle.

(c) Creep.19%.

((1) Breaking load.8839 kg.

With the exception of creep, which would be expected to be high in a cut fibre rope, these properties closely approach the ideal combination of properties sought in ropes.

What I claim is:

1. Multistrand laid ropes composed of films, ribbons or filaments of stereoregular polypropylene having a combination of properties which in the form of the standard 3 inch circumference laid rope are (1) a stretch resistance at 5,000 lbs. (2268 kg.) load of at least 400 lbs. (181 kg.) per 1% extension, (2) a torque resistance of at least in.-lb. (0.58 kg.-m.) per revolution, per tan strand helix angle, (3) a creep after 120 repeat loadings to of 9 the breaking load of less than 15% and (4) a breaking load of at least 7.75 tons (7874 kg).

2. Ropes according to claim 1 wherein the stereoregular polypropylene is isotactic polypropylene.

3. Ropes according to claim 1 which have a weight per 100 feet of less than 18.5 lb. (8.4 kg.).

4. Rope yarns adapted for use in construction of ropes according to claim 1 comprising continuous filaments, said yarns having a friction of at least 2 lb. (910 g.) and a resilience of 5055% when the yarn rigidity is 1200- 2000 g. wt. cm. or a resilience of 65-85% when the yarn rigidity is 600-1200 g. wt. cm.

5. Rope yarns adapted for use in construction of ropes according to claim 1 comprising slit films or ribbon filaments, said yarns having a friction of 45-40 lbs. (2.0- 18.1 kg).

6. Rope yarns according to claim 5 having a resilience of 85-100% when the yarn rigidity is 200-600 g. wt. cm.

10 or a resilience of 65-85% when the yarn rigidity is 600- 1200 g. wt. cm.

7. Rope yarns according to claim 6 wherein the friction is 1030 lbs. (4.513.6 kg).

References Cited UNITED STATES PATENTS 2,979,774 4/ 1961 Rusignolo. 3,007,765 11/1961 Ruyter et al. 3,054,652 9/ 1962 Huemann et al. 3,112,300 9/1963 Natta et al. 3,266,232 8/1966 Dawbarn et al.

FOREIGN PATENTS 1,209,985 3/ 1960 France.

813,891 5/1959 Great Britain.

FRANK J. COHEN, Primary Examiner.

WERNER H. SCHROEDER, Assistant Examiner. 

